1. Field of the Invention
This invention pertains to a method of cooling and dispensing beverage, and to apparatus for cooling and dispensing beverage in which the beverage is precooled before admittance into a storage reservoir; the dispensing rate is far greater than the refill rate.
2. The Prior Art
Cold beverages, be they carbonated or non-carbonated, are preferably served at a temperature as close to freezing as is possible. Specifically the preferred serving temperature is as close to 32 degrees F. (0 degrees C.) as is possible. The highest acceptable temperature of dispensed beverage per the standards for the soft drinks of the Coca-Cola Company, the Pepsi-Cola Company, 7-UP Company, Dr. Pepper Company, Royal Crown Cola Company and their many competitors is 40 degrees F. (4.4 degrees C.). A temperature higher than this is considered unsatisfactory.
As the beverage temperature becomes higher, ice is needed in the cup and the beverage then becomes diluted with melting ice water. Off-taste is a problem from melting ice water, foaming and loss of carbonation is a further problem.
Ideally a soft drink should be dispensed at 32 degrees-36 degrees F. (0 degrees-2.2 degrees C.); 40 degrees F. (4.4 degrees C.) is the upper limit of acceptabilty. It is very difficult to attain 32 degrees F. (0 degrees C.) dispensing because this is at the freezing point of water and refrigeration controls and temperature controls are unable to reliably maintain this temperature without occasional freeze-ups. An ice bank type beverage cooler and dispenser can attain dispensing temperature at or close to 32 degrees F. (0 degrees C.) with the use of relatively massive quantities of ice, but an air-cooled or direct refrigerant cooled beverage cooler and dispenser can reliably attain only 36 degrees-40 degrees F. dispensed beverage.
The normal-desired carbonation for cola, lemon-lime, root beer, and most soft drinks other than orange is 3.5 to 4.5 volumes of carbon dioxide gas in the finished drink. Carbonation devices and systems are very sensitive to water or beverage temperatures. For example, at 36 degrees F. (2.2 degrees C.), 18 PSIG (1.27 kg/sq cm) carbon dioxide pressure gives 3.5 volumes of carbonation; at 46 degrees F. (7.8 degrees C.), 25 PSIG (1.76 kg/sq cm) is necessary to obtain 3.5 volumes. In post-mix soft drink dispensing, 5 parts of carbonated water are mixed with 1 part of non-carbonated syrup and the carbonation of the mixed drink ends up being about five-sixths of the carbonation of the water Specifically, if a carbonation of 3.5 volumes is wanted, the carbonated water must have 4.2 volumes. In order to attain 4.2 volumes at 36 degrees F. (2.2 degrees C.), a pressure of 25 PSIG (1.76 kg/sq cm) is required. However, as water warms up the pressure must be increased or the attained carbonation falls off. For example, 25 PSIG (1.76 kg/sq cm) at 42 degrees F. (5.6 degrees C.) gives 3.8 volumes which dilutes to 3.1 volumes in the finished drink, and 25 PSIG (1.76 kg/sq cm) at 48 degrees F. (8.9 degrees C.) gives 3.4 volumes which dilutes to 2.8 volumes in the finished drink, 25 PSIG (1.76 kg/sq cm) at 54 degrees F. (12.2 degrees C.) gives 3.0 volumes which dilutes to 2.5 volumes in the finished drink.
In commercial and factory soft-drink cooling, carbonation and dispensing systems, these physical constraints imposed by water, syrup, pressure and temperature are met with concentrated and relatively expensive hardware which bring horsepower, high pressure, booster pumps, large heat exchangers and other special and relatively expensive hardware to bear upon these problems. The constraints are solved with costly componentry.
What we have been trying to do for several decades is to devise a low-cost, reliable, simple, relatively un-complicated method and apparatus for cooling, carbonating and dispensing soft drinks, the kind of method and apparature that can be used in a home, or a professional office, or for weekend parties.
One such recent attempt is that of John R. McMillin as is shown and taught in his co-pending patent application U.S. Ser. No. 453,183 filed on Dec. 27, 1982. This particular system has a miniature refrigerator cabinet with a 30 watt 0.04 HP) electro-mechanical compressor. This is the smallest compressor available in the world as of this date. Within a cooling compartment is an evaporator which cools air in the cooling chamber. Within the cooling chamber are three syrup reservoirs, each of which holds about 1/2 gallon (1.9L) of soft drink syrup. Also within the cooling chamber is a combination water reservoir and carbonator. The reservoir is closed and pressurized with carbon dioxide gas and sized to hold about 5 gallons (18.9L) of water. The reservoir has a float and needle valve fill control connected to a water supply line. An outlet from the reservoir goes to a dispensing nozzle.
The carbonation pressure upon the reservoir and the water therein is at 25 PSIG (1.76 kg/sq cm) constant and the thermostat is pre-set to maintain the water at about 35 degrees F. (1.7 degrees C.). When this system is initially filled with water and syrup, it takes about 72 hours for the water and syrup to be cooled and carbonated to produce a drink at 36 degrees F. (2.2 degrees C.). This system produces an excellent finished beverage with a reliable 3.5 volume of carbonation and 36 degrees F. (2.2 degrees C.) temperature.
The problem is lack of dispensing capacity. As drinks are dispensed, cold carbonated water is drawn out of the reservoir and is replaced by relatively warm non-carbonated water which needs to be cooled and carbonated. The refilling rate is far in excess of the cooling capacity of the refrigeration system and the water in the reservoir increases in temperature and decreases in carbonation until the system can no longer dispense a satisfactory drink. As this machine was embodied, it could dispense up to twenty 6 oz. (177 ml) drinks before the carbonated water became too warm and the carbonation became too low. Specifically, dispensing of 3540 ml of beverage withdraws 2950 ml of water from the reservoir. After replacement of the 2950 ml of cold carbonated water with warm non-carbonated water, the water in the reservoir warms up to 41.2 degrees F. (5.1 degrees C.) and has at the most 3.8 volumes of carbonation. The dispensed drink will be at 40.2 degrees F. (4.6 degrees C.) or higher and have 3.2 or less volumes of carbonation. When ice is placed in the drink, the temperature will go down, but the flavor and carbonation both become diluted.
One method that has been utilized to increase the dispensing capacity of this unit is to shut off the water inlet. Then you can dispense the entire contents without dilution, warm-up and carbonation loss. The problem with this is that it is a nuisance and the refrigeration capacity, during the period in which the water is shut off, is lost. After dispensing, when the water line is then turned back on, the refrigeration starts itself. The dispenser will have to recover itself during the night and on following days.
It can be seen that this system works and dispenses well, but it does not have sufficient dispensing capacity to enable it to utilize and dispense its cooled and carbonated contents.